LEARNING OUTCOMES

Understand the meaning of the terms biodiversity, population, habitat,

environment, community and ecosystem

Ecology is the study

of communities in their environment

community the total number of organisms from

all the populations in an area

the number of one type of organism (species)

in an area

population

A group of organisms with similar characteristics that

can interbreed to produce fertile offspring

species

These are the non-living, physical parts of the environment, including:

• Wind

• Water

• pH

• Light

• Temperature

These are the living parts of the environment, including:

PREDATORS DISEASE

WASTE PRODUCED BY

LIVING ORGANISMS

What is an

Ecosystem?

An ecosystem is the name given to all the living things, community, and their environment in a particular area.

LEARNING OUTCOMES

• Understand that the Sun is the source of energy for most ecosystems on Earth

• Understand the role of green plants as producers in capturing this energy and making it available to other organisms

• Understand food chains and webs and be able to identify producers, consumers and trophic levels;

The living organisms are all dependent on each other through feeding relationships.

However, all life on Earth relies on the energy from the Sun.

Energy flow • Life can exist on Earth

because of sunlight energy.

• Plants capture light energy through the process of photosynthesis.

• And make organic compounds such as carbohydrates

The compounds made by plants are eaten by other organisms, so plants make the sunlight

energy available to other organisms.

Primary consumers eat green plants.

Tertiary consumers

eat secondary consumers.

Secondary consumers

eat primary consumers.

The sequence of producers trapping the

Sun’s energy and this energy then

passing on to other organisms as they

feed is known as energy flow.

The sequence can be drawn as a food

chain with arrows from producer to

consumers.

The arrows represent the direction of the energy flow.

A food chain

Primary

consumer Producer

leaf caterpillar bird cat

Secondary

consumer

Tertiary

consumer

• Put the organisms in the sort cards into the correct sequence.

• Write down the food chains that you have made.

• Can you label the food chain using terms you have learned?

Omnivores eat both animals and

plants.

Herbivores

eat only

plants.

Carnivores eat only animals.

The different stages in the feeding

sequence are called TROPHIC LEVELS

(or ‘feeding levels’).

The first organism in the food chain (the

producer) is TROPHIC LEVEL 1

The second organism in the food chain (the

primary consumer) is TROPHIC LEVEL 2

etc

FEEDING POSITION

TROPHIC LEVEL

Most organisms will not feed

on only one other organism.

This means that food chains

are interlinked to form

food webs.

What would happen if all of the grass died?

What would happen if the grass died?

• The grass is the producer, so if it died the consumers that feed on it - rabbits, insects and slugs - would have no food.

• They would starve and die unless they could move to another habitat.

• All the other animals in the food web would die too, because their food supplies would have died out.

• The populations of the consumers would fall as the population of the producer fell.

What would happen if the population of slugs decreased?

• Slugs, rabbits and insects all eat grass.

• If there were fewer slugs there would be more grass for the rabbits and insects.

• With more food the populations of rabbits and insects would increase.

• However, the thrushes would have to eat more insects to maintain their population, so it is also possible that the population of insects could decrease.

• This in turn may reduce the populations of voles and frogs.

What would happen if the population of insects decreased?

• There would be more food for the rabbits and slugs, so their populations would increase.

• However, there would be less food for the frogs and voles, so their populations would decrease.

• This means less food for the foxes and hawks.

• However, there are likely to be more rabbits and thrushes for them to eat, so their populations are likely to stay the same.

What would happen if a disease killed

all of the snakes?

________________________________

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What effect would there be if, due to

poor spring weather, the rowan flowers

were not fertilised?

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LEARNING OUTCOMES

• Construct pyramids of numbers and biomass as models of food chains and explain the difference

• Explain the advantages and disadvantages of each type of pyramid

• Understand the difficulties caused by organisms feeding at two different trophic levels.

Pyramids of numbers

• The number of organisms at each stage of a food chain (i.e. at each trophic level) can be represented by a pyramid of numbers.

• Each bar represents a trophic level and is drawn the same height.

• The width of the bar represents the number of organisms at that trophic level.

• There are fewer organisms at each level because energy is lost by each organism.

DE

CR

EA

SIN

G N

UM

BE

RS

& E

NE

RG

Y

Draw Pyramids of Numbers for the following data.

Organism Stinging nettle plants

Caterpillars Robin

Numbers 15 12 1

Organism Single hawthorne

bush

Caterpillars Dunnock

Numbers 1 12 1

The problem with a pyramid of numbers

is that it is not always pyramid-

shaped, as it does not take into

account the size of the organisms

involved, e.g. one oak tree will support

many more organisms than one

grass plant

Inverted

pyramid of numbers

Pyramids of numbers that include parasites may appear top heavy, as many parasites will feed on

one consumer.

Advantages & Disadvantages of Pyramids of Numbers

ADVANTAGES DISADVANTAGES

Easy to count Ignores sizes of organisms

No organisms get killed Difficult to convert e.g. grass plant leaves to

numbers which can be worth comparing with

others

Biomass represents chemical energy stored in the organic matter of a trophic level.

The units of a pyramid of biomass are

units of mass per unit area,

often grams per square meter (g m-2)

or as energy content, (joules, J)

The biomass is found by measuring the dry mass of the organisms at each trophic level. This requires

killing the organisms.

Pyramids of biomass

Use the data below to draw a Pyramid of Biomass

for the hawthorne Pyramid of Numbers you drew previously.

Organism Single hawthorne

bush

Caterpillars Dunnock

Biomass/J 75 000 7 200 680

Advantages & Disadvantages of Pyramids of Biomass

ADVANTAGES DISADVANTAGES

Amount of energy in a trophic level more accurately

represented

Organisms must be collected and killed in order to measure

biomass.

Difficult to catch/weigh all organisms

The biomass of an individual can vary throughout the year,

e.g. an oak tree will have a much greater mass in June

than December

Another difficulty in producing both pyramids of number and biomass arises

if organisms feed at two different trophic levels e.g. an organism that eats

both plants and animals.

QUESTION 4 HOMEWORK booklet

http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/

Chose: food chains, energy, biomass, cycles< energy in biomass < activit

LEARNING OUTCOMES

Use data to interpret and explain in terms of the amount of energy available at each trophic level, decreased due to heat from respiration, excretion and egestion and uneaten structures,

and understand why shorter food chains are more efficient

http://www.ricksastro.com/terra/moth.jpg

This owl pellet contains fur and bones of a mouse

Energy loss & trophic levels

Most food chains are relatively short, with just four organisms.

This is because at each stage of energy transfer (including trophic level 1), some energy is lost.

Not all of the energy from the Sun is trapped by producers. This is because:

• light is reflected from leaves

• light passes through leaves and misses chloroplasts

• light energy is used to evaporate water from leaves.

Energy loss at trophic level 1

The transfer of energy between plants and animals and between animals of different trophic levels is usually 10 – 20%.

This means that for every 100g of food material available, only between 10 and 20g is used to build animal tissue (as ‘biomass’) in the primary consumer’s body.

Energy loss at other trophic levelS

The loss of energy between plants and consumers and between consumers is due to

three main reasons:

1. Not all the available food is eaten.

Most carnivores do not eat the skeleton or fur of their prey, for example.

2. Not all the food is digested

some is lost as faeces in egestion.

3. A lot of energy is lost as heat in respiration. Respiration provides the energy for movement, growth, reproduction etc. Heat is produced as a by-product of respiration. Heat is lost and cannot be passed on to the next trophic level.

Energy Flow

& excretion

& undigested material

including heat

& movement

Calculate the percentage of the energy taken in by the caterpillar which is

used for growth

ENERGY IN = 200J

ENERGY USED IN GROWTH = 33J

PERCENTAGE = 33/200 x100

= 16.5%

Calculate the energy lost in respiration and

the percentage used to make new tissue.

Calculating energy efficiency

This bullock has eaten 100kJ of stored energy in

the form of grass, and excreted 63kJ in the form of

faeces, urine and gas. The energy stored in its

body tissues is 4kJ. So how much has been used

up in respiration?

The energy released by respiration

= 100 – 63 – 4 = 33kJ

Only 4 kJ of the original energy available to the

bullock is made into new tissue and is available to

the next stage, which might be humans.

The percentage of the original energy used to

make new tissue

= 4/100 X 100 = 4%

The percentage of the original energy used to

make new tissue is known as the

energy efficiency of an organism.

Energy efficiency

This is the percentage of the energy that an organism consumes

that is used to make new tissue.

15

316

1890

11,977

6

x

1095

5465

respir

ation

decay

TOTAL = 6612 kJ TOTAL =

Shorter food chains

Food production is more efficient if the food chain is short,

because a higher percentage of energy is available to us.

http://www.bbc.co.uk/bitesize/ks3/science/or

ganisms_behaviour_health/food_chains/revi

sion/8/

http://www.bbc.co.uk/bitesize/ks3/science/or

ganisms_behaviour_health/food_chains/revi

sion/9/

LEARNING OUTCOMES

Use and construct keys to identify organisms and classify them into

major groups based on the observable features.

• Keys are used to identify unknown organisms.

• Dichotomous keys, used in biology, consist of a series of two part statements that describe observable features of organisms.

• At each step of a dichotomous key you are presented with two choices. As you make a choice about a particular feature or characteristic of an organism you are led to a new branch of the key. Eventually you will be led to the name of the organism that you are trying to identify.

ACTIVITY: constructing a key

1. Give your group of items a name, e.g. leaves, branches and write this at the top of a poster page

2. Write descriptive words on the post-its for each of the items in your bag, keep them with the item they describe.

3. From your descriptions find one observable feature which you can use to divide the items into 2 groups

4. Write the feature on your poster below the name and draw to lines from it, one to the left the other to the right.

5. Write your decision on these lines, e.g. yes, no; 2, more than 2…

6. Divide your items into the 2 groups.

7. Look at each group separately and again use your descriptions to divide the items into 2 groups based on a single observable feature.

8. Repeat steps 4-6

9. Continue until each group has only one item and stick k this down on the poster

A branching key:

A numbered key:

• Carefully examine and think about the observable features of the 8 aliens and create a dichotomous key using some of these characteristics.

Broad leaved trees

This trees leaves are green all over and have a hairy upper surface. They are rounded with a pointed tip and they are larger on one side of the midrib than the other. The edges of the leaves are toothed, but they have no lobes or prickles. The stalk is short and rounded and bears a single leaf.

LEAF LITTER

This wingless invertebrate has a waistless segmented body with 3 pairs of legs. It uses a spring under its abdomen to move by jumping.

Grassland

This 6 legged invertebrate has a broad body with a triangle shape on its back. It has 2 pairs of wings; one pair forms a protective case. It moves by flying or walking and has no obvious snout.

Garden weeds

This spineless weed has smooth edged, arrow shaped leaves. The stem trails along the ground and produces pink and white trumpet shaped flowers.

LEARNING OUTCOMES

Understand why classification is needed for: Ÿ identification Ÿ the study of how organisms have changed through time Ÿ the comparison of biodiversityŸ conservation of species

3. Viruses are a complex group and are very difficult to classify. All viruses, e.g. the HIV virus that causes AIDS, lack proper cellular organisation. They have a DNA/RNA core (DNA and RNA are nucleic acids – the building blocks of chromosomes) and an outer protein coat without the typical cytoplasm of other cells. They can only live if they gain access to other cells and many biologists therefore regard them as non-living.

LEARNING OUTCOMES

Use observations of organisms to help describe the main features of the five kingdoms (protoctista, bacteria, fungi, plants and animals), to include:Ÿ

– mode of nutritionŸ

– cell wall Ÿ

– cellular organisation

All living organisms are divided into five large groups called Kingdoms.

The 5 kingdoms are:

All the organisms in each kingdom have specific features in common.

These include:

1. their mode of nutrition (how they feed)

2. whether they have a cell wall

3. cellular organisation;

Group Nutrition Cell wall Cellular organisation

Protoctista Saprophytic or photosynthetic

Cellulose cell wall or none

Single celled with nucleus or algae that are not truly multicellular

Bacteria Saprophytic Non-cellulose Single celled with no nucleus

Fungi Saprophytic or parasitic

Non-cellulose Single or multicellular – can be ‘acellular’ with it being difficult to distinguish individual cells and nuclei scattered throughout the organism

Plants Photosynthesis Cellulose Single or multicellular – ‘typical’ cell arrangement with a nucleus

Animals Eating organic food None Single or multicellular – ‘typical’ cell arrangement with a nucleus

Use the table to complete the classification poster

in your booklet

fungal cell

dead food

1. Enzymes released

onto food

2. Enzymes digest food

3. Soluble

products

absorbed

LEARNING OUTCOMES

Understand the difficulties in classifying:Ÿ • species as a group of organisms, with

shared features,Ÿ which can breed together to produce fertile offspring Ÿ

• viruses, which lack cellular organisation and are therefore considered by many biologists as non-living,

• and understand that classification systems change over time;

1. Some organisms are difficult to classify e.g. Euglena, which has both plant and animal characteristics. This is why single-celled plants and animals are classified in a separate group called the Protoctista.

2. Sometimes it is difficult to identify which species an organism belongs to or where one species merges into another.

Definition – a species is a group of organisms, with shared features, which can breed together to form fertile offspring.

QUESTION 3 HOMEWORK booklet

LEARNING OUTCOMES

Use appropriate sampling techniques to investigate changes in the distribution of organisms within a sample area, limited to quadrats, pitfall traps, pooters and nets

LEARNING OUTCOMES

Measure biotic and abiotic factors, such as wind speed, water, pH, light, temperature and biodiversity (the number of plant and animal species)

Finding out about populations in a habitat

Fieldwork provides information about what plants and animals live in a particular habitat and their numbers. This can be used to measure biodiversity.

It is therefore necessary

• to be able to identify organisms, using keys

• and understand the different sampling

techniques used to count them.

We cannot actually count every plant or animal in a

particular place, so

we count a sample of the population to calculate

an estimated population size.

Sampling populations

You should understand the importance of random sampling.

This is essential to avoid observer bias.

WHAT DOES THIS MEAN? This means that the person collecting the data

does not affect the result deliberately, e.g. by only counting in one part.

Quadrats are usually used

to count plants,

but can also be used

to count slow moving

animals

such as snails.

1. Lay out two tapes at right-angles in the area you

want to sample.

2. Use random number tables to pick co-ordinates:

• quadrats should be placed randomly so that a

representative sample is taken.

3. Place a quadrat (of suitable size) at that point and

count the organisms within it.

4. Repeat using using at least 20 quadrats, at other

random coordinates across the grid:

• repeating increases the reliability.

• collecting across the whole grid area reduces the

effect of an unusual distribution

5. Calculate the average number of organisms in each

quadrat

6. Use the average to calculate an estimated total

number of organisms in the grid area.

Quadrats can be used to estimate a population in an area which is fairly uniform. Examples include lawns, woods and open ground.

There are three ways to count organisms to estimate population size:

• 1. Density

(calculating the number of organisms per m2);

• 2. Frequency

(number of number of quadrats that contain the organism)

• 3. Percentage cover

(estimating the percentage of the grid area that contains the organism)

Percentage cover – do you agree with the estimates?

• Percentage cover is an easy way to estimate population size.

• However, a disadvantage is that it is difficult to estimate exactly what percentage of the quadrat is actually covered by a particular type of plant, so it is normal to round up to the nearest 10%. An exception is if there are any plants with a percentage cover of 1 -5% - this is recorded as 1 and not 0.

• This makes the results less reliable than estimating the density.

Belt transects can be used to

investigate

changes in the distribution

of organisms along a

particular habitat,

e.g. due to changing abiotic

factors such as light intensity

On the seashore a belt transect can be

used to investigate the effect drying out,

due to tidal changes, has on the different

species found as you move inshore.

Sampling animal populations

How do we know that the invasive

harlequin ladybird is affecting the

populations of native ladybirds?

used to collect small

invertebrates.

• Sweep nets allow you to collect large numbers of invertebrates that live in low vegetation (stems, tall grasses, flowers etc) or in rivers and ponds

• Sweep netting involves making a large rapid sweep with a net in between large paces.

• The invertebrates can be collected in a tray and counted

Pitfall traps must be properly set up:

• the top of the jar should be level with the soil surface

• cover the trap with a stone or piece of wood to keep out the rain, to make it dark and to stop birds eating your catch

• the traps must be checked often to avoid the animals escaping or being eaten before they are counted

• as with most methods a large number of traps makes results more reliable and minimises the effects of unusual results

Stones to prevent rain flooding the trap or birds or other

predators from removing the trapped animals

jar sunk in a hole in the ground

• http://www.bbc.co.uk/scotland/learning/bitesize/standard/biology/biosphere/investigating_an_ecosystem_rev5.shtml

LEARNING OUTCOMES

Use data collected (primary or secondary) as evidence to account for the distribution of organisms

Account for this distribution in terms of the adaptations of the organisms found to their environment and competition for resources, which can affect population growth, (water, light, space and minerals in plants and water, food, territory and mates in animals

LEARNING OUTCOMES

Evaluate the validity and reliability of data collected during fieldwork when drawing conclusions about the methods of data collection and environment;

See worksheet (pages 54 -55 textbook)

Each organism is adapted (suited) to the environment in which it lives.

This case study tries to explain why specific plants live at different distances from the seashore.

1. Describe the area that was being studied.

2. What sampling method was used to study the distribution of plants along the sand dunes?

3. How many samples were taken?

• 1km sand dune, divided into 3 sections.

• Section 1 from the start of the first sand dune inshore.

• Section 2 half way between 1 and 3.

• Section 3 from the end of the last dune to to the start of the woodland.

• 3 interrupted belt transects

• 20 at each site

4. Name the biotic data collected.

5. Name the abiotic data collected

• the average percentage cover

• of marram grass, common heather and gorse

• along each transect

• average light intensity reaching the ground

• Average soil moisture

• Average pH

6. Describe the conditions in which each of the plants prefers to grow.

• Marram grass: can grow in very unstable conditions such as those found near the shore, where the sand is constantly moving in the wind. It helps to stabilise the dunes, by holding the sand together for other plants to grow in.

• Heather: small shrub, prefers stable moist soil

• Gorse: large shrub, prefers very stable soil with lots of moisture and nutrients

7. Describe the trends shown by the graphs.

• Marram grass is only common in transect 1

• Heather is not found in transect 1 but is found in transect 2

• Gorse is most common in transect 3, but uncommon or absent at transects 1 and 2.

8. Use the biological knowledge about the 3 plants and the abiotic data to explain the trends.

• Marram grass can grow at the beginning of the dunes where there is not much water available in the sand, 20%.

• It needs high light intensity to grow, 95%.

• Further inland, where the conditions are more stable, there is less light and there is more moisture, so the other plants out-compete the marram grass.

• Heather cannot grow in transect 1 because there is not enough moisture.

• Gorse grows best in transect 3 where there is most water, 60%.

• Gorse is a large shrub and creates shade, preventing the marram grass and heather from growing.

9. What features of this investigation make the results reliable?

• The plants were counted in 20 quadrats at each transect and an average was calculated.

11. Explain why you think this a fair test?

12. State the following:

the independent variable

the dependent variable

the controlled variables

• Only one thing was being changed.

• The position of the transect along the dune.

• Percentage plant cover in each quadrat

• Size of the quadrat

• Time of the year the measurements were taken.

It was not possible to keep the wind, light intensity, soil moisture or pH controlled. However these factors were measured and helped to explain the presence or absence of the plants at the different transects.

QUESTIONs 1&2 HOMEWORK booklet

LEARNING OUTCOMES

Use mathematical models to explain changes in populations

Explain the consequences of changes in population density on the environment, to include birth and death rates, emigration and immigration

Population changes

Population numbers change over time.

Many factors can contribute to population change but they can be summarised by:

This can be written as an equation:

Population growth =

(birth rate + immigration) –

(death rate + emigration)

Number

of

organisms

lag

phase

stationary

phase

exponential

phase

death

phase

A population growth curve shows the numbers of organisms

in a population over time.

Describe and explain what is happening to the

population in each area of the graph:

Think about:

What

abiotic and biotic

factors might affect the

organisms to cause

any change in

population size?

Is the population

increasing,

decreasing or

staying constant?

Population numbers will also be affected by:

• Some animals are prey to others, eg rabbits are the prey of foxes. The fox is a predator. The predator must kill the prey for food. This increases the population of predator but will decrease the population of prey.

• The populations of a predator and its prey can be measured over many years.

• The following graph shows the changes in populations of hares and lynxes over 40 years.

lynx snowshoe

hare

ANSWERS There are 2 main patterns:

• The populations of each animal remains steady over the 40 years, increasing and decreasing between certain limits.

• Changes in the population of one organism affects the population of the other organism. – When the lynx population increases, the hare population

decreases. This is because there are more hares being eaten.

– When the hare population decreases the lynx population decreases as there is less food to eat.

– When the lynx population decreases the hare population increases as there are fewer being eaten.

HUMAN POPULATION GROWTH

REASONS FOR INCREASING HUMAN

POPULATION GROWTH

The Age-Sex

distribution for an

expanding

population, such

as developing

countries in Asia,

Latin America and

Africa

The large

percentages of

the population in

the youngest

ages assures that

these populations

will expand as

most of its

population moves

into the

reproductive ages

The Age-Sex

distribution for a

stable population,

such as U.S.,

Western Europe

and other

developed

countries

The bulge of the

population in the

middle ages

means most of

the population will

be leaving the

reproductive ages

and growth will

slow.

Read through your notes on classification before answering

question 3 (p71) in the

GCSE Biology textbook.